Weird EGT readings

ArttuH · Post by **ArttuH** » Wed Aug 16, 2006 9:34 am

I have some trouble to get EGT logging working properly. During first tests I noticed that readings are a bit strange. At room temperature readings were slightly too high and at high temperaturtes readings were clearly too low. At first I thought that thermocouple amplifier would be the reason but its output looked right. For troubleshooting I configured the Megatune to show raw ADC values of EGT input and then I fed 0V and 5V directly to processor pin. The raw ADC values for these voltages were 14 and 153 instead of 0 and 255. So clearly there is something wrong.

All other analog inputs works just fine and all supply voltages are ok so I think that there isn't anything wrong with the PCB. I have also tried another processor with same results. Any ideas what could be the reason?

Oh, I almost forget to mention that I'm using MSnS-E 029q with MT 2.25.

daxtojeiro · Post by **daxtojeiro** » Wed Aug 16, 2006 2:17 pm

when you checked this was your ground connected to the same ground point as the MS ECU?
Phil

ArttuH · Post by **ArttuH** » Wed Aug 16, 2006 9:25 pm

daxtojeiro wrote:when you checked this was your ground connected to the same ground point as the MS ECU?
Phil

Yes, I used the same ground. I took these 0V and 5V directly from the PCB so they are exactly the same than the ground and supply of the processor.

ArttuH · Post by **ArttuH** » Thu Aug 17, 2006 9:17 am

Ok, problem solved! And now I'm feeling pretty stupid. I was using wrong pin, that one next to right one. Obiviously there was some current leak between the pins, just enough to change the voltage on floating pin and to give some changing readings.

Morten VJ · Post by **Morten VJ** » Thu Aug 17, 2006 12:10 pm

One suggestion clean the board, or you wil spendt a lot of time hunting ghosts

BR

Morten

ArttuH · Post by **ArttuH** » Thu Aug 17, 2006 9:28 pm

Don't worry, I will

The board is still in early testing phase so I haven't yet cleaned it from flux residuals.